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Nov 28, 2012 3:00pm PST
expression. ( drumbeats ) taxation without representation: copley's father-in-law, an english merchant, was importing tea to america. copley felt he could not speak out against his family, nor could he defend them. seeking his artistic heritage, he sailed for europe. it wasn't long before he became part of that heritage, a forerunner in the great romantic movement. still, the longer his self-imposed exile in england, the greater his loneliness. his children were his models. the commissions continued. but his greatest masterpieces were painted while memory and imagination were fresh. ( drumbeats, lively trumpet notes ) in his isolation in england, copley worked harder to be america's first great painter. "poor america," he wrote, "yet certain i am she will finally emerge from her present calamity and become a mighty empire. and it is a pleasing reflection that i shall stand amongst the first of the artists that shall have led the country to the knowledge and cultivation of the fine arts." narrator: ...yet george catlin had a grander dream: he was an artist in search of a cause. ( native
Nov 29, 2012 8:00am PST
of newton's laws? neptune, gang. neptune. so they call this neptunium. first element beyond uranium and that's neptunium 239. it's got a very, very short half-life. and you know what it does? it decays. and guess what it emits? begins with a b. no, not alpha. try it again. it emits a beta particle. okay. it emits a beta particle. and what does it turn into? how many people can figure out what the number is here that couldn't do it before but maybe now can? show of hands. four people. wonderful. now, how many? what is it gonna be, gang? it's 94. 94, 94. what is the second planet that we named after discovering by newton's laws? it wasn't neptune, it was what? - pluto. - pluto. guess what we'd be calling this, gang? plutonium. plutonium. pu239. and you know what plutonium will do? plutonium as well as uranium 235 will undergo fission when a neutron taps it. and so this is used for power production. u235, used for power production. historically, when the bombs were dropped back in world war ii, the bomb that devastated hiroshima was a uranium 235 bomb. you know how much uranium 235 was left aft
Nov 30, 2012 3:00pm PST
groups still farming the lands of mesoamerica. concepcion rash, with her daughter-in-law isabelle, prepares the evening meal. they cook over a wood fire, beneath a thatched roof, much the same way that the three-stoned hearth was used at ceren 14 centuries ago. the rash family is mainly self-sufficient. they teach their children and grow their food, all within a short distance of the home. as in ancient times, daily life revolves around the household. [ baby crying ] anthropologist richard wilk. there's a lot of good reasons for people here to want to live in a multiple-family household like this. there's a lot of jobs that have to be done every day, both by men and women -- washing, hauling corn in from the field, cutting firewood. these kinds of things take time every day. and if you're off working in the fields, you can't do them. by having multiple-family households like this, they can divide up the labor. [ speaking native language ] interpreter: what can i say ? it's a lot easier working together. without a helper, life is much harder. since we're at home, we can help each o
Nov 28, 2012 8:00am PST
square law, twice as far away, 1/4 the effect, okay? so as these things get further and further away, the electrical force kind of peters down. but the strong interaction really, really peters down. and that means you can't really have a very big atomic nucleus. and here's why. let's suppose you have a big nucleus as this big. you got a proton over here and protons over here, they're so far apart. the nuclear interaction between these two is almost trivial. but between these two of the electric compulsion is not trivial. and so what happens? very, very large nucleus, just by virtue of the spreading apart, are unstable nuclei and that's beyond 83, atomic number 83. every atomic nucleus above atomic number 83 is unstable. and in that environment, you have then the ejection of alpha, beta and gamma particles. so it's almost simple geometry. right now, this particle we'd call an alpha particle. this is a helium nucleus. and i'll write that helium nucleus like this. and i'll put a two down here and a four here. and this nomenclature, i hope you're familiar with. this is simply the atomic
Dec 5, 2012 8:00am PST
postulate: all the laws of physics will be seen to be the same in uniformly moving reference frames. this is moving uniformly with respect to this. in fact, einstein said, it makes no difference whether this is at rest and this is moving or this is at rest and this is moving away. motion really is relative. it's a relative motion between the planet and the ship. so, let me ask you a question. these six minute flashes that the ship really is sending-- really is sending the six, we agreed on that before-- these six minute flashes are gonna be seen how long apart by that person back here, who's now looking, who puts the telescope up and takes a look? check your neighbor. what's the answer, gang? - 12. - 12. you see that. i mean if 6 is seen as 12, then 6 will be seen as 12. so we can complete this diagram up here and say this. we have another planet here. a person watching these flashes, okay? what happens? really the flashes are like this, okay? they're all scrunched up in here and all dragged out here. and so, six minutes will be seen three for approach, but for a recession, 12 minut
Search Results 0 to 4 of about 5